There exist many applications, for example, individual lighting systems, where a rechargeable electric battery is charged by means of a photovoltaic module.
Conventionally, a circuit for charging an electric battery by means of a photovoltaic module comprises:
a DC/DC switched-mode power converter having input terminals coupled to the terminals of the photovoltaic module and output terminals coupled to the terminals of the battery; and
a control circuit capable of controlling the switched-mode power converter to transfer electric power from its input terminals to its output terminals, that is, from the photovoltaic module to the battery, to charge the battery.
Generally, the control circuit is coupled across the battery for its power supply.
A problem which is posed is that when the battery is untimely disconnected, that is, while the photovoltaic module is still connected to the input of the charging circuit and the control circuit is active, that is, it controls the switched-mode power converter to transfer electric power from its input terminal to its output terminals, there exists a high risk of destruction of the charging circuit, and in particular of the switched-mode power converter control circuit.
To limit this risk, manufacturers of this type of charging circuits advocate never disconnecting the electric battery from the charging circuit without having previously disconnected the photovoltaic module.
There however always remains a risk for such a recommendation not to be followed by the user.
It would thus be desirable to have a circuit for charging an electric battery by means of a photovoltaic module, the circuit being intrinsically protected against an untimely disconnection of the battery.